Monobore completions result in a common diameter of the well from the surface using expansion techniques. Usually a string has a recess at its lower end representing a zone of enlarged diameter at its lower end. When that string is secured in position another string is run through it and the top end of the second string is placed in alignment with the recess at the lower end of the first string. An expansion device is then applied to the second string to make its inside diameter approximately the same as the inside diameter of the upper string. The two strings are secured to each other in the recess of the upper string. Because of the recess, the expansion of the lower string results in no internal dimension reduction in the overall assembled strings.
One way to do this is to mount a recess on the lower end of the upper string and expand the upper string to the recess and then put the lower string into position adjacent the recess of the upper string and expand the lower string. Another way is to form the recess downhole. One such technique is described in the July 2005 edition of World Oil article by Fischer and Snyder a technique of forming a bell at the bottom and then continuing liner expansion to the surface was described. This bottom up technique puts the tubular being expanded into compression and risks buckling during the expansion. What is needed and not provided by this technique is a way to expand from top to bottom with the string in tension and a simple technique of transitioning between swages after the tubular is expanded so that the recess can then be produced. This is more technically challenging to do than a bottom up expansion because in a top down expansion there has to be a swage transition to a bigger size within an expanded tubular to form the even larger recess. A technique of disabling the larger swage until the recess needs forming is also incorporated into the invention. Features are also provided for emergency release in case the expansion assembly cannot fully advance and needs to be pulled out of the hole to the surface. These and other advantages of the present invention will be more apparent to those skilled in the art from a review of the description of the preferred embodiment and the associated drawings while recognizing that the claims define the full scope of the invention.